Indicating fuse



y 1937. L. A. KAUFFMAN' 2,079,214

INDICATING FUSE Filed June 5, 1936 Patented May 4, 1937 PATENT OFFICE INDICATING FUSE Leroy A. Kauffman, Washington, D. 0., assignor to Indicating Fuse Manufacturing Corporation, Washington, D. 0., a corporation of Delaware Application June 5, 1936, Serial No. 83,756

8 Claims.

The present invention relates to electric fuses and more particularly to visible indicating fuses of the plug type, which when a short circuit occurs, gives off continually a visible signal indicating the ruptured and blown condition of the fusible element, having amongst its principal objects the provision of an indicator fuse of this character wherein the various parts or elements thereof may be easily handled and readily assembled, thereby materially reducing the cost of manufacture thereof and rendering the same commercially desirable.

A further object of the invention is the provision of a molded casing for indicator fuses which can, be produced in one piece of insulating material and yet properly house the indicator and fusible element therefor, thereby not only reducing the cost of making the casing, but eliminating the necessity of making the casing in sections, whereby theindicator and fuse element may be placed therein and further, considerably reducing the cost of assembling the various parts or elements of a fuse indicator.

A still further object of the present invention 5 is to provide a locking key for indicator fuses which when applied, will effect a connection between the indicator and the fusible link with the terminals of the fuse and further will lock the same in place within the fuse shell or cas- 3() ing without the aid of solder or other bonding or connecting agents.

Other objects of the invention will be in part obvious and in part pointed out hereinafter.

In order that the invention and its mode of operation may be readily understood by persons skilled in the art, I have in the accompanying illustrative drawing and in the detailed following description based thereupon, set out an embodiment of the same.

In the drawing:

Figure 1 is a vertical section through the indieating fuse embodying the present invention.

Figure 2 is a sectional perspective view of the fuse casing or shell, the locking key, disc and rivet therefor disassembled therefrom and showing by dotted lines the direction of movement of the key, disc and rivet to the shell when applying the same thereto, and

Figure 3 is a bottom plan View of the fuse casing.

Referring now more particularly to the accompanying drawing wherein I have shown one way of carrying out the present invention and in which drawing like and corresponding parts are -designated by similar reference characters throughout the several views, the fuse comprises a casing or shell molded in one piece of suitable insulating material such as bakelite, porcelain and the like. The top portion or head I of the casing is preferably of a disc configuration having formed therewith and projecting from the opposite faces thereof a substantially tubular stem 2. The upper end of this stem is opened and has formed therein a lamp compartment 3, whereas a rivet opening 4 is formed within 1 the lower end of this stem.

Formed with and depending from the lower face of the head portion l of this shell is an annular flange or skirt 5 which is arranged concentrically with and spaced from the stem 2 in 15 order to establish a fuse link compartment 6 therebetween. Also formed with this shell are a pair of radially extending and spaced partitions 1' which connect with the stem 2 and. the flange 5 for establishing a groove 8 therebetween, which groove extends within and communicates with the lamp compartment 3. The stem 2 is provided with an opening 9 which extends in alignment with the groove 8 and also communicates with the lamp compartment 3. The lock- 25 ing key I0, preferably made from a flat strip of fibre, has an enlarged portion H which is seated within the groove 8 and a reduced end portion 12 which extends through the lamp compartment 3 into the opening 9 of the stem 2. The 3D outer wall of this key ID has projections l3 formed therewith which act as threads for receiving the correspondingly shaped grooves of the brass contact shell M for the purpose of attaching this shell M to the casing l and prevent its withdrawal therefrom without unscrewing the same.

The threaded shell It serves as one contact terminal for the fuse and is provided with a flange I5, which latter retains a fibre disc 16 in 40 place upon the lower end of the casing I. This fibre disc i6 is provided with a central opening H which when appliedto the casing receives the lower tapered end iii of the stem 2. A brass rivet 19 which serves as a central contact ter- 45 minal for the fuse is seated within the opening d of the stem 2 and is retained therein by fiattening or riveting the inner end of the rivet as is illustrated in Figure 1 of the drawing.

The visible indicator herein employed is a low 5 potential neon glow lamp 20. In assembling the fuse, this lamp 2B is inserted within the lamp compartment 3,so. that it will assume a vertical position therein and a signal light given off there! from will emit through the outer opened end of 55 the lamp compartment formed within the stem 2. When the lamp is inserted within the fuse casing, one terminal thereof and herein indicated by the numeral 2 i, will project through the opening 9, whereas the other terminal 22 of the lamp will extend through the groove 8 and have contact with the upper edge of the shell l4. When the key In is inserted within the fuse casing in the manner as illustrated in Figure l of the drawing, the leads or contact terminals of the lamp will have a wedging contact between the key l0 and the casing for retaining these leads 2| and 22 within the opening 9 and the groove 8 respectively. A resistor 23 is carried by this key l0 and establishes an electrical connection between the lead 2| of the lamp and the inner end of the contact rivet IS. The resistance herein employed consists pref erably of a composition painted or otherwise applied to the outer extremity of the portion l2 of the locking key and acts as a leak resistance which permits only a minute quantity of current to pass into the glow lamp 20 and at the same time, protect the electrical circuit to which the fuse is applied so as to prevent injury to any delicate instruments or electrical apparatus included in such circuit.

A fuse link 24 is positioned within the fuse compartment 6 having one of its extremities secured by wedging contact between the lower face of the end l2 of the locking key and the upper end of the rivet IS. The opposite or free extremity of this fuse link after passing around the stem 2 within the fuse compartment 6 extends through a slot 30 formed within the lower face of the flange 5 and then upwardly between the outer face of the flange 5 and the inner face of the threaded shell H. The free extremity of the lead 22 and the upper extremity of the fuse link 24 which have contact with the shell l4 are permanently connected thereto by means of solder 25, which lat ter also effects a binding engagement between the shell l4 and the fuse casing I so as to prevent the rotation of the shell I 4 upon the fuse casing, The outer face of this casing I has ribs 26 formed therein which act as a handhold, whereupon the fuse may be screwed within or removed from the fuse socket of the cutout base and further, provide means whereby suitable markings for the fuse may be embossed or in any other suitable manner be placed thereupon.

From the construction and arrangement of parts herein set forth, it will be readily understood that I have presented a fuse casing which can be molded in one piece of insulating material and the various parts of the fuse as well as the indicator therefor may be inserted within this casing and locked in position therein with only one bonding agent, such as the solder 25, and fur ther, that the various parts of the indicator and fuse may be easily and readily assembled by the average person without the aid of any special tools.

In molding a plug fuse casing with screw threads thereon, the threads that retain the threaded shell I4 thereon add greatly to the molding cost of the casing in that a multiple mold is required. By providing the threads 13 upon the locking key, corresponding threads upon the casing l are dispensed with and yet the shell l4 may be properly retained upon the casing 1. Therefore, this key !0 not only provides a means for retaining the shell l4 upon the casing I but provides a carrier for the resistor and further, provides means for locking the lamp 20 and one end of the fusible element 24 to the central contact or rivet I 9.

The disc l6 provides a closure for the lower end of the fuse compartment 6 and a vent opening is established between the outer edges of this disc and the lower end of the flange 5 so that the burnt gases from the fuse compartment may readily escape around the outer edges of this disc l6 and between the outer wall of the flange 5 and the shell l4.

Manifest ly, the construction herein shown is ca.- pable of considerable modification and such modiflcations as come within the scope of my claims, I consider within the spirit of my invention.

I claim:-

1. A fuse unit comprising a shell, contact terminals carried by said shell, a fuse link, a removable locking key, a resistor carried by said key, a glow lamp indicator having one of its leads connected to one of said contact terminals and the other of said lamp leads being connected through said resistor to the other of said contact terminals.

2. A fuse unit comprising a hollow shell, contact terminals therefor, a fusible link, a locking key for connecting one end of said fusible link to one of said contact terminals, means whereby said locking key will retain the other of said contact terminals upon said shell and other means for connecting the opposite end of said fusible link to said last mentioned contact terminal upon said shell.

3. A plug fuse comprising a casing, a central contact mounted therein, a contact shell surrounding said casing, a fuse link arranged within said casing, a locking key for connecting one end of said fuse link with said central contact,

means for connecting the opposite end of said fuse link to said contact shell and said contact shell having engagement with said locking key whereby the same will be retained upon said cas- 4. A plug fuse comprising a casing, a fuse link arranged within said casing, a rivet contact secured within said casing, a threaded contact shell arranged about said casing, said casing having a radially extending slot formed therein,

a locking key insertable through said slot for connecting said fuse link to said contact rivet, means for connecting said fuse link to said threaded contact shell, threads formed with said locking key and engageable with said threaded contact shell for retaining the latter around said casing.

5. An indicating fuse unit comprising a casing having a lamp compartment and a fuse compartment formed therein, a fuse link arranged within said fuse compartment, a. lamp having lead wires extending therefrom arranged within said lamp compartment, contact terminals and a locking key for electrically connecting the wire leads of said lamp to said contact terminals.

6. An indicating fuse comprising a casing having a fuse compartment, a fuse link arranged therein, said casing having a vertically arranged lamp compartment formed therein communicating with said fuse compartment, a lamp having wire leads extending therefrom and positioned within said lamp compartment, a central contact, a threaded shell contact, a locking key, a. resistor electrically connecting said central contact with one lead wire of said lamp, the other lead wire of said lamp being eletrically connected to said threaded contact shell, and means whereby said locking key will effect a connection between said fuse link and said central contact.

7. An indicating plug fuse comprising a. casing, a hollow stem formed therewith, a rivet contact received within one end of said stem, a lamp arranged within said stem, a flange formed with said casing and extending concentrically about said stem for providing a fuse compartment therebetween, a fuse link arranged within said fuse compartment, a contact shell arranged about said flange, a locking key for connecting said contact shell to said flange, means for electrically connecting said fuse link with said contacts, and means for connecting said lamp to said contacts but in parallel with said fuse link whereby when the latter becomes blown a visible signal will be given off by said lamp.

8. An indicating fuse comprising a casing molded in a single piece of insulating material, a stem forming a part of said casing, an annular flange arranged concentrically about and spaced from said stem forming an opened end fuse link compartment, a disc for closing the opened end of said fuse link compartment, a signal lamp arranged within said stem, a fuse link arranged within said fuse link compartment, a central contact terminal carried by said stem, a threaded contact shell arranged about said flange, a looking key insertable within said casing for retaining said threaded contact shell thereupon, a resistor carried by said locking key, means for connecting said fuse link in series with said contact shell and central contact and said lamp and resistor in series with said contacts but in parallel with said fuse link whereby when said fuse link becomes blown said lamp will visibly indicate its ruptured condition.

LEROY A. KAUFFMAN. 

